Thermalization of an impurity cloud in a Bose-Einstein condensate

TL;DR

This paper investigates how impurity atoms thermalize within a Bose-Einstein condensate, revealing velocity-dependent effects on depletion rates and condensate cooling through a Boltzmann equation approach.

Contribution

It introduces a Boltzmann equation framework to analyze impurity thermalization in BECs, highlighting velocity-dependent behaviors and cooling effects.

Findings

Below Landau critical velocity, impurity depletion slows down.

High velocities increase impurity depletion.

Multiple collisions can optimize condensate cooling.

Abstract

We study the thermalization dynamics of an impurity cloud inside a Bose-Einstein condensate at finite temperature, introducing a suitable Boltzmann equation. Some values of the temperature and of the initial impurity energy are considered. We find that, below the Landau critical velocity, the macroscopic population of the initial impurity state reduces its depletion rate. For sufficiently high velocities the opposite effect occurs. For appropriate parameters the collisions cool the condensate. The maximum cooling per impurity atom is obtained with multiple collisions.